1. Field of the Invention
The present invention relates to a document reading apparatus to read a document for an image processing apparatus such as a scanner, a printer and a copier.
2. Description of the Related Art
A document reading apparatus is known which comprises a housing having on an upper surface thereof a document support platen formed of a transparent glass plate for supporting a document, and which also comprises a document reading unit provided in the housing and including a CIS (Contact Image Sensor) for scanning and reading a document placed on the document support platen. For example, each of Japanese Laid-open Patent Publications 2001-24843 and 2001-75194 discloses a document reading apparatus with an document pressing device for applying pressure to the surface of a document so as to bring the document in intimate contact with a contact glass plate, thereby preventing the document, even if e.g. partially curled, from locally rising away from the document support platen.
The above-described conventional document reading apparatus are basically suited to read a document in sheet form, but not in book form, as will be described in detail below. FIG. 6 is a schematic perspective view of a scanner as a representative conventional document reading apparatus which corresponds to the above-described patent publications, and which has a document support platen G supporting a book BD to be opened and read as a document placed thereon. Referring to FIG. 6, when the book BD is opened and placed on the document support platen G formed of a transparent glass plate, the book BD in the middle (at the spine) between adjacent open pages is most likely to stay away from intimate contact with the document support platen G, so as to locally rise away from the document support platen G. An image of a page of the book BD read using this scanner causes a resultant printed image at the risen portion of the book BD to be deformed (distorted) or black due to loss of light reflected from the book BD, preventing a good print image.
For solving this problem and obtaining a good print image, pressure P may sometimes be applied onto the spine of the book BD from above to press the book BD downward to the document support platen G However, this may damage the book BD, and may not be able to completely solve the problem of the black image and the image deformation.